A magnetic recording medium comprising a non-magnetic support having coated thereon a coating composition of ferromagnetic particles of acicular crystals such as .gamma.-Fe.sub.2 O.sub.3 or CrO.sub.2 dispersed in a binder, followed by orientation, has widely been used for recording and reproducing.
Recently, it has strongly been desired to improve recording density in order to record large volume of information and to minimize the size of magnetic recording devices. Therefore, it is necessary that the maximum dimension (diameter) of acicular magnetic particles be much smaller than the wavelength to be recorded or the length of a recording bit in order to prepare a recording medium suitable for high density recording using conventional acicular magnetic particles. These days, acicular particles having a dimension (diameter) of 0.3 .mu.m have been commercially realized and the minimum wavelength typically recorded is about 1 .mu.m.
It is necessary to further reduce the acicular magnetic particle size, for example, to particles having a diameter of 100 .ANG. or less and having a particle volume of 10.sup.-17 cm.sup.3 or less, in order to obtain a medium useful for higher density recording. However, magnetic characteristics deteriorate, because such particles are easily affected by heat and the surface area of the particles becomes smaller, and magnetic orientation is difficult to successfully carry out when a magnetic field is applied to a magnetic layer.
In this connection, a magnetic recording medium containing hexagonal crystallized ferrite having a tabular shape and have an axis of easy magnetization in a direction vertical to its table, which is subjected to magnetic orientation in a machine direction has been found, as disclosed, for example, in Japanese Patent Publication (unexamined) Nos. 6525/83 and 6526/83, and U.S. Pat. No. 4,425,401.
A magnetic recording medium containing hexagonal crystallized ferrite has made it possible to realize high density recording, but there is still a problem in that video output is not sufficient.